This invention relates generally to devices and methods for aiding the moving and installation of equipment. Specifically, the present invention is related to a caster with an integral leveling component.
Equipment, particularly heavy equipment, is often supplied with two mechanical components that aid in moving and installation. These are casters and levelers, respectively. A caster generally comprises a wheel mounted on a chassis capable of swiveling 360 degrees. Levelers generally comprise a threaded stud and a foot that are connected by means of a ball-socket joint. They serve to establish a level, final height of a unit and secure it with respect to the ground. Installing these components may be complicated, especially when the equipment is vulnerable to tipping during movement.
Placement of levelers and casters is governed by three competing constraints: stability, adjustability, and clearance. Stability refers to the overall equipment stability: that is, ensuring that the equipment does not tip over easily. To achieve maximum equipment stability, the devices that support the equipment should be positioned as far as possible from the equipment""s center of gravity. Adjustability refers to the ability to access the leveler for adjustment once the unit is put into place. For instance, if the unit is intended to mate to another unit or occupy space against a wall, a leveler may become inaccessible if it is positioned in a corner. Clearance refers to the placement of the casters and levelers relative to each other. In particular, it is essential that the casters do not interfere with the levelers as the casters swivel about 360 degrees during movement of the equipment.
These constraints can create a real problem for a designer or engineer when both casters and levelers are desirable in the application. For example, to achieve maximize equipment stability when the levelers are used, the levelers should ideally be positioned in the corners of the equipment. However, to minimize the chance of the equipment tipping during movement of the equipment, the casters should also occupy the corner positions. Obviously, with standard casters and levelers, it is not possible to have both the casters and the levelers in the same corner position. To compound the problem of achieving stability, reducing unit footprint is often of competitive advantage and of critical marketing importance in many applications. A good example can be found in the semiconductor industry. Here, the size of processing equipment is scrutinized because it will likely occupy clean-room space that costs a premium per unit area. Semiconductor equipment must also comply with rigorous safety specifications such as SEMI, which mandates stability at a 10 degree tilt angle. However, if the unit""s footprint is reduced there may be little room for both casters and levelers to be placed in a stable configuration. As a result, expensive solutions, such as retractable booms and counterweights, are often employed that far exceed the cost of the casters and levelers themselves.
Traditional, separate casters and levelers suffer from additional technical and cost disadvantages. In order for the leveler stud to be well-supported when the weight of the equipment rests on the levelers, it is typical to incorporate a machined support that extends below the base of the frame. The drawback of this design is that the leveler cannot be retracted very far off the ground. Thus, when the unit is moved, not only does the leveler cause the unit to have poor ramp clearance, the leveler is unprotected and vulnerable to damage by striking obstacles. To mitigate this problem, designers often will choose more expensive leveling components with larger stud diameters and far greater load capacities than are necessary to support the unit.
Another potential problem with separate casters and levelers is the inability to adjust the leveler from the top. The ability to adjust a leveler from the top is especially desirable in high technology applications. However, in many current designs that use traditional, separate casters and levelers, the levelers cannot be adjusted from the top because in order to achieve overall unit stability the design requires that the leveler be placed interior to a vertical frame member of the supported unit.
Finally, it is expensive to properly install traditional, separate casters and levelers. In a typical high quality installation, several custom machined parts must be made to provide proper support. In addition to the cylindrical support for the leveler, a plug is often machined to incorporate this support into the base of the vertical tube member and a gusset that straddles the two corner members of the frame base is often required to support the caster. All these parts must be jigged and welded in place on a custom basis. If these parts can be eliminated the cost savings can be substantial.
Combination casters and levelers do exist. Some of these devices place a leveler between separated wheels to allow for retraction of the leveler. However, the separation of wheels results in a loss of load capacity and usually requires the use of a non-standard leveler with a smaller floor contact area than is provided by a standard leveler. Other combined caster and leveler devices achieve leveler clearance by incorporating a large wheel offset, using very small wheels, using a non-standard leveling component, placing the leveler offset from the swivel axis of the caster, or using a combination of the foregoing. These designs often have significant disadvantages that may outweigh the benefits of the combination, including decreased load capacity, poor handling, large size, awkward appearance, increased potential for floor damage, impractical leveler adjustment, high cost and unpredictable leveler location.
The present invention integrates a caster and a leveler that are very similar in design to standard casters and levelers. The combination offers moving and support capability in a one-piece assembly no larger than an ordinary caster. The integrated device is simple in design and has widespread application wherever a design requires both casters and levelers.
This integrated caster and leveler assembly generally comprises a wheel chassis, a thrust bearing assembly, and a leveling sub-assembly disposed within an internally threaded and proximally located tubular member, such as a kingpin rivet. The integrated caster and leveler assembly may combine these and other elements to reliably aid in the transport and installation of various types of equipment. If a kingpin rivet is used, a base plate may be included to facilitate attachment to the supported equipment. The base may be a rectangular plate and may have mounting holes for screws and the like that attach to a frame member of the unit. The base may also be a corner bracket to take full advantage of caster and leveler integration and allow maximum stability and leveler adjustability. Alternatively, the outer surface of the tubular member may be threaded to allow the device to be mounted to the equipment.
The thrust bearing assembly generally comprises an upper and lower raceway supporting an upper and lower set of ball bearings, a shim for proper bearing spacing, and an o-ring seal that protects it from environmental contamination.
The integrated device includes elements similar to high quality dual bearing casters; however, the integrated device includes the internally threaded tubular member, and has a wheel chassis with a slightly larger offset (the distance from the swivel axis to the wheel axis) than is found in most standard casters. These features allow the leveling sub-assembly to thread through the tubular member. The leveling sub-assembly is similar to a standard leveler and comprises a stud, a foot, and a locknut. However, the foot attaches to the stud by a ball-socket joint, which rotates with three rotational degrees of freedom, or is otherwise attached to achieve at least two rotational degrees of freedom, and ideally pivots very smoothly, even at a high pitch angle. As the leveler is retracted, a portion of the foot will contact the circumference of the wheel and pivot so that the opposite edge of the foot pitches upward, away from the wheels. Significantly, this allows the leveler to be aligned with the swivel axis while maintaining close proximity to the caster wheels. Additionally, these features allow the wheels of the caster to be placed close together without placing the leveler at a substantial offset from the swivel axis, thus improving load capacity over combined caster and leveler devices that place the leveler between separated wheels. They also allow the distance between the leveler and casters to be reduced while maintaining approximately standard-sized wheels and leveler footpads.
In use, when retracted, the leveler foot responds dynamically to changes in the direction of motion of the unit such that the leading edge of the foot is always higher than the trailing edge. This offers two technical advantages compared to standard casters and levelers that substantially reduce the risk of damage to the equipment and to the leveler. First, ramp clearance is greatly improved due to the pitched foot and its proximity to the caster wheels. Second, the leveler is effectively braced against the wheel or wheels insulating the stud from damage and providing better distribution of impact loads.
The device may be designed so that in the fully retracted position, the leveler foot is pitched upwards to a selected nominal pitch angle that is less than a selected maximum pitch angle. This maximum pitch angle should be selected to be at or less than the angle at which the foot may bind, swivel may be impeded and/or the foot may eject from the ball end of the stud. For a given wheel size, the dimensions of the stud may be selected so that the pitch angle of the foot rests at this nominal pitch angle and never exceeds the maximum pitch angle in the fully-retracted position. This ensures smooth, non-binding interaction between the wheels and leveler foot as the wheel swivels and the foot pivots about the longitudinal axis of the leveler stud. Furthermore, small mechanical features that differentiate the leveler from a standard leveler may be included in the design. These features include a small shoulder between the hex portion and the ball-end of the stud and a curved rim on top of a tongue that circumscribes the socket of the foot.
For overhead adjustability, the upper end of the stud may include an appropriately sized hex socket, much like a set screw. The stud can also have a hex portion that permits bottom adjustment with a wrench. The locknut may be a standard nut and serves to secure the leveler once installation is complete it should be noted that while most applications of the claimed device would be in industry to move and support heavy manufacturing equipment, xe2x80x9cequipmentxe2x80x9d as used herein includes any object that needs to be moved and/or supported, in any environment. For example, and without limitation, this device could be used on beds and other furniture, vending machines, home appliances and pianos. In summary, this invention comprises a leveling assembly combined with a caster to create a one-piece assembly with the characteristics of both. The design has a number of advantages including, but not limited to, a single purchased part, improved stability, better leveler adjustability, a compact assembly, leveler protection, and a lower cost of installation. The nature of the present invention will be more readily understood after consideration of the drawings and the detailed description of the preferred embodiment that follow.